Induction of retinal pigment epithelial cells from monkey iPS cells

The induced pluripotent stem (iPS) cell is expected to be a powerful tool for research and development in regenerative medicine. Previously, the authors reported that human iPS cells differentiated into retinal cells, including photoreceptors and retinal pigment epithelial cells. In this study, they produced iPS cell lines from monkeys to investigate their ability to differentiate into retinal cells.

To generate iPS cells, the fibroblasts derived from cynomolgus monkey abdominal skin were infected with retroviruses carrying Oct3/4, Sox2, Klf4, and c-Myc genes and then were cultured on STO feeder cells. Next, the established iPS cells were cultured with the conditioned medium of PA6 cells to induce RPE cells. The properties of the differentiated RPE cells were analyzed.

Approximately 1 month after viral infection, some epithelial-like colonies appeared among the fibroblasts. These colonies were morphologically similar to the cynomolgus embryonic stem (ES) cell and expressed ES cell-specific markers. By producing teratomas in SCID mice, these cells were confirmed to have the ability to differentiate into three germ layers. In addition, the RPE cells induced from the monkey iPS cells had characteristic polygonal shapes and pigments. These cells expressed RPE cell-specific markers such as RPE65, CRALBP, Bestrophin 1, and MERTK and exhibited phagocytotic function in vitro.

The RPE cells derived from monkey skin with iPS cell technology can be used for autologous or allogeneic transplantation to test the possibility of immune rejection and to evaluate their function in vivo with the same techniques that will be used in clinical trials.